1. Field of the Invention
The present invention relates to a bearing device having a function of reducing axial runout in a fluid bearing of a general industrial machinery or the like.
2. Related Background Art
Spindle motors having enhanced bearing rigidity are known, parallel provided with magnetic bearings so as to strengthen the rigidity of an air fluid bearing portion of an air spindle motor as described in a document entitled “NTN Corporation Technical Review No. 69, Development of Magnetic aerostatic hybrid spindle.”
Further, measures for accurately detecting rotor position and controlling roller posture while configuring a magnetic bearing have been proposed, as disclosed in Japanese Patent Application Laid-Open No. H11-311511. With a conventional technique proposed in the development of aerostatic hybrid spindle in the above document, deviations in a shaft surface processed with high precision are detected by a positional sensor, and control is performed so as to reduce the shaft deviations. However, extremely minute shaft deviations equal to or less than the surface roughness of the shaft fall within an error range, and there is a problem in that minute shaft deviations cannot be handled.
Further, with the magnetic bearing disclosed in Japanese Patent Application Laid-Open No. H11-311511, a shaft center position is detected directly by a scanning probe microscope that are disposed on both ends of the shaft, and the bearing itself is configured by magnetically coupling alone. Therefore, there is a problem in that the device itself becomes a large-scale device.